This invention relates to shot for use in shotguns. In particular, the invention relates to shot having a metallic core made of lead or lead alloy.
Spent lead shot lying on the ground can be a problem to birds. Such spent shot is often picked up or "mouthed" with gravel by the birds and may also be swallowed and taken into the gizzard of the bird. The lead from the shot is broken down and absorbed by the bird often in lethal doses.
Spent lead shot lying on open ground can also be an environmental problem with the lead leaching and causing toxic poisoning of the ground or of water sources or being digested by birds.
Attempts have been made in the past to alleviate this problem by coating the individual shot pellets with a barrier layer to prevent the toxic lead from being absorbed into the ground or into birds digesting the shot pellets. However existing coating techniques have not proved to be completely successful since known coatings can be worn or ground away by the abrasive action of a bird's gizzard.
Known coating techniques generally involve coating lead or lead alloy shot with at least one layer of wear-resistant non-toxic coating material acting as a shield or barrier to the toxic lead or lead alloy core. The known coating materials suitably comprises a solid film lubricant, e.g. polytetrafluoroethylene or molybdenum disulphide. Solid film lubricant is the preferred known coating material since it is both non-toxic and inert and thus reduces the harm to the environment caused by spent shot. Ideally each pellet is coated with a coherent or continuous coating of the coating material. Different coating materials may be applied in different coating operations, e.g. by a dip, barrel or spray process. To assist adhesion of such coatings, adhesive resins may be employed. The coating applied to each pellet may not be thick, e.g. from 0.01 to 0.02 mm.
Although known coatings applied to shot are not intended to damage the environment, they do not discourage birds and the like from actually digesting the shot when the shot has been used and is lying on the ground. If so digested the coating can become removed, resulting in the lead being absorbed into the bird.